Sir W. Harris on the Laws and Operation of Electrical Force. 73 



therefore, are as the square roots of the Surfaces and boundaries 

 conjointly, according to the formula C=\/S.B, as also verified 

 in the preceding experiment 9. 



A double surface, therefore, having a double boundary, takes a 

 double charge, but not otherwise. Neglecting all considerations of 

 the boundary, therefore, the surface and boundary varying together, 

 the charge in this case will be as the surface directly. 



18. The author having verified experimentally the laws of surface 

 and boundary, as regards plane rectangular surfaces, proceeds to 

 consider the charges of square plates, circular plates, spheres, and 

 closed and open surfaces generally. 



Experiment 1 1 . Plate 10 inches square, surface 100 square inches, 

 boundary 40 inches, compared with a similar plate 14 inches square, 

 surface 196 square inches, boundary 56 inches. Here the surfaces 

 are as 1 : 2 nearly, whilst the boundaries are as 1 : V2 nearly. 



In this case charge of square plate, surface 100 square inches, was 

 found to be 8 circular inches under an intensity of 10°. Charge 

 of the plate, surface 196 square inches, 11 circular inches, under 

 the same intensity of 10°. Here the charges are as 8 : 11, whilst the 

 surfaces may be taken as 1 : 2, that is to say (neglecting the boundary), 

 the charges are as the square roots of the surfaces, according to the 

 formula C= VS • 



On examining the intensities of these plates, they were found 

 to be inversely as the surfaces ; thus 8 circular inches upon the plate 

 surface 100, evinced an intensity of 10° ; 8 circular inches upon the 

 plate, surface 196, evinced an intensity of 5° only, or \ the former, 



according to the formula E =— . 



S 



Experiment 12. A circular plate of 9 inches diameter, surface 

 63*6 square inches, compared with a circular plate of 18 inches, or 

 double that diameter, surface 254 square inches. Here the surfaces 

 are as 1 : 4, whilst the boundaries or circumferences are as 1:2. 



Charge of 9-inch plate, 6 circular inches, under an intensity of 

 10°. Charge of 18-inch plate, 12 circular inches, under the same in- 

 tensity of 10°. Here the charges are as 1 : 2, whilst the surfaces are 

 as 1 : 4 ; neglecting the difference of boundary, therefore, the charges, 

 as in the preceding experiments, are as the square roots of the 

 surfaces. 



On examining the intensities of these plates, they were found to 

 be inversely as the surfaces ; thus 6 circular inches upon the 9-inch 

 plate evinced an intensity of 10°, as just stated; 6 circular inches 

 upon the 18-inch plate had only one-fourth the intensity, or 2°*5, 



being inversely as the surfaces, according to the formula E=^« 



Experiment 13. A circular plate of 9 inches diameter, surface 

 63*6 square inches, compared with a circular plate of 12*72 inches 

 diameter, surface 12 7' 2 square inches. Here the surfaces are as 1 : 2. 



Charge of 9-inch plate (surface 63*6 square inches), 5 circular 

 inches, under an intensity of 8°. Charge of 12* 72-inch plate (sur- 

 face 127'2 square inches), 7 circular inches, under the same intensity 



